The present invention relates to a cutting machine having a cutting means that comprises a rotary blade, for cutting a workpiece such as a semiconductor wafer.
As known to people of ordinary skill in the art, in the production of semiconductor chips, a plurality of rectangular regions are sectioned by streets arranged on the surface of a semiconductor wafer in a lattice form, and a semiconductor circuit is formed in each of the rectangular regions. The rectangular regions are separated from one another by cutting the semiconductor wafer along the streets to produce semiconductor chips. To cut the semiconductor wafer along the streets, a cutting machine that is also called xe2x80x9cdicerxe2x80x9d is used. The cutting machine has a chuck means for holding a workpiece to be cut, that is, a semiconductor wafer and a cutting means for cutting the semiconductor wafer. The cutting machine further comprises a first moving means for moving the chuck means relative to the cutting means in the first direction, a second moving means for moving the cutting means relative to the chuck means in the second direction perpendicular to the first direction, and a third moving means for moving the cutting means relative to the chuck means in the third direction perpendicular to the first direction and the second direction. The cutting means comprises a rotary blade which is mounted rotatably on the center axis of rotation extending in the second direction. This rotary blade has a shape of an annular thin plate and is disposed perpendicular to the second direction. By moving the chuck means relative to the cutting means in the first direction, the circular peripheral portion of the rotary blade is applied to the semiconductor wafer to gradually cut the semiconductor wafer in the first direction. The cutting line of the semiconductor wafer is defined by the position of the rotary blade in the second direction. The cutting depth of the semiconductor wafer is defined by the position of the circular periphery of the rotary blade in the third direction.
It is important that the cutting of the semiconductor wafer should be carried out along the streets with strict accuracy. It is important that the cutting depth should be also set to a required value sufficiently precisely. It is therefore important that the position of the rotary blade in the second direction should be set fully accurately and that the position of the circular periphery of the rotary blade in the third direction should be set fully accurately. Accordingly, in a conventional cutting machine, when a rotary blade is newly set, a dummy wafer held on the chuck means is actually cut upon using the above new rotary blade to observe the cutting line of the dummy wafer, thereby detecting the accurate position of the rotary blade in the second direction. For the observation of the cutting line of the dummy wafer, there can be used a so-called alignment means that is used for detecting the position of each street of the semiconductor wafer held on the chuck means. The alignment means comprises a microscope arranged opposite to the surface of the semiconductor wafer, an imaging means for imaging an optical image input into the microscope and an image processing means for making required processing such as binary processing on an image obtained by the imaging means. Meanwhile, as for the position of the circular periphery of the rotary blade in the third direction, the rotary blade is moved in the third direction to bring the circular periphery thereof into contact with the surface of the chuck means to define the reference position thereof.
The making and setting of the rotary blade are inevitably accompanied by an error even though it is a slight degree. It is necessary therefore to carry out the above-described relatively troublesome operation for the accurate positioning of the rotary blade each time the rotary blade is exchanged. Further, when cutting is carried out repeatedly, the rotary blade is inevitably worn down and hence, the above-described relatively troublesome operation must be also carried out after cutting has been performed a required number of times.
Further, in the conventional cutting machine, the degree of abrasion of the rotary blade is checked with the naked eye and the rotary blade is exchanged when considerable abrasion is observed. The above observation with the eye is troublesome and requires skill.
It is therefore the principal object of the present invention to provide a novel and improved cutting machine which can set the position of the rotary blade in the second direction, that is, the cutting line of the rotary blade fully accurately without requiring troublesome operation such as the cutting of a dummy wafer.
It is another object of the present invention to enable to set the position of the circular periphery of the rotary blade in the third direction, that is, the cutting depth of the rotary blade fully accurately without requiring troublesome operation, in addition to the above principal object.
It is a further object of the present invention to enable to detect the abrasion of the rotary blade automatically, in addition to the above principal object and the another object.
According to the present invention, the above principal object is attained by providing a rotary blade detection means capable of detecting the position of the rotary blade in the second direction. The above another object and further object of the present invention are attained by enabling the rotary blade detection means to detect the position of the circular periphery of the rotary blade in the third direction as well.
That is, according to the present invention, the cutting machine for attaining the above principal object of the present invention comprises a chuck means for holding a workpiece to be cut, a cutting means for cutting the workpiece held on the chuck means, a first moving means for moving the chuck means relative to the cutting means in the first direction, and a second moving means for moving the cutting means relative to the chuck means in the second direction perpendicular to the first direction, the cutting means being constituted by a rotary blade mounted so as to rotate on the center axis of rotation extending in the second direction, wherein
the cutting machine further is provided with a rotary blade detection means capable of detecting the position of the rotary blade in the second direction.
The cutting machine for attaining the above another object and further object comprises a third moving means for moving the cutting means relative to the chuck means in the third direction perpendicular to the first direction and the second direction, the rotary blade is shaped like an annular thin plate perpendicular to the second direction, the cutting depth of the workpiece is defined by the position of the circular periphery of the rotary blade in the third direction, cutting is carried out by moving the chuck means relative to the cutting means in the first direction, and the rotary blade detection means can also detect the position of the circular periphery of the rotary blade in the third direction.
Preferably, the rotary blade detection means is constituted by a first microscope having an optical axis perpendicular to the second direction, a second microscope having an optical axis perpendicular to the third direction, an imaging means for imaging an optical image input into the first microscope and an optical image input into the second microscope selectively, and an image processing means for processing an image obtained by the imaging means. Preferably, the optical axis of the second microscope is parallel to the second direction. The workpiece may be a semiconductor wafer which has a plurality of rectangular regions sectioned by streets formed on the surface in a lattice form and semiconductor circuits formed in the respective rectangular regions, and which is cut along the streets.